How to create vector representation of roadmap like scans
It turned out that my intuition was not far off. The skeletonization is a good step. The Hough transform though is not a good way to create a graph of the roadmap. It seems that the Ramer–Douglas–Peucker algorithm can help out here. This algorithm first takes all the skeleton pixels as input, and sees this as a starting graph. The algorithm then proceeds to remove intermediary pixels that do not add information to the shape of the graph.